6.1.2.2
CT earthing direction
M13048-29 v13
To make the restricted earth fault protection REFPDIF operate correctly, the main
CTs are always supposed to be star -connected. The main CT's neutral (star)
formation can be positioned in either way,
ToObject
or
FromObject
. However,
internally REFPDIF always uses reference directions towards the protected
transformers, as shown in Figure
. Thus the IED always measures the primary
currents on all sides and in the neutral of the power transformer with the same
reference direction towards the power transformer windings.
The main CT's connection type can be freely selected for each of the involved
current transformers.
6.1.2.3
Railway specific applications for REFPDIF function
GUID-F8184D63-C28F-4016-BDE8-CD1B081105CA v1
If appropriate configuration and settings are applied, the REFPDIF function can
also be used for the following special applications in the railway supply system:
•
Defrost protection, when a single phase differential protection is temporary
arranged among two CTs during de-icing operation of the catenary contact line
wires.
•
Single phase differential protection applied across one winding (i.e. either over
one single-phase transformer winding or a generator winding).
6.1.3
Setting guidelines
IP14942-1 v1
6.1.3.1
Setting and configuration
M13052-3 v3
Recommendation for analog inputs
M13052-8 v10
ISI: Neutral current input.
I2P: Phase currents from winding HV side current transformer set.
Recommendation for Binary input signals
M13052-17 v8
BLOCK: The input will block the operation of the function. It can be used, for
example, to block the operation during special service conditions for a limited time.
Recommendation for output signals
M13052-21 v9
START: The start output indicates that
Idiff
is in the operate region of the operate-
restraint characteristic.
TRIP: The trip output is activated when all operating criteria are fulfilled.
DIROK: The output is activated when the directional criteria has been fulfilled.
BLK2H: The output is activated when the function is blocked due to high level of
second harmonic.
1MRK 506 375-UEN A
Section 6
Differential protection
Railway application RER670 2.2 IEC
77
Application manual
Summary of Contents for RELION RER670
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